Zhao Lina, Cánovas-Márquez José T, Tang Xin, Chen Haiqin, Chen Yong Q, Chen Wei, Garre Victoriano, Song Yuanda, Ratledge Colin
State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu, 214122, People's Republic of China.
Departamento de Genética y Microbiología (Unidad asociada al IQFR-CSIC), Facultad de Biología, Universidad de Murcia, 30071, Murcia, Spain.
Appl Microbiol Biotechnol. 2016 Feb;100(3):1297-1305. doi: 10.1007/s00253-015-7079-y. Epub 2015 Oct 28.
Fatty acid biosynthesis in oleaginous fungi requires the supply of reducing power, NADPH, and the precursor of fatty acids, acetyl-CoA, which is generated in the cytosol being produced by ATP: citrate lyase which requires citrate to be, transported from the mitochondrion by the citrate/malate/pyruvate transporter. This transporter, which is within the mitochondrial membrane, transports cytosolic malate into the mitochondrion in exchange for mitochondrial citrate moving into the cytosol (Fig. 1). The role of malate transporter in lipid accumulation in oleaginous fungi is not fully understood, however. Therefore, the expression level of the mt gene, coding for a malate transporter, was manipulated in the oleaginous fungus Mucor circinelloides to analyze its effect on lipid accumulation. The results showed that mt overexpression increased the lipid content for about 70 % (from 13 to 22 % dry cell weight, CDW), whereas the lipid content in mt knockout mutant decreased about 27 % (from 13 to 9.5 % CDW) compared with the control strain. Furthermore, the extracellular malate concentration was decreased in the mt overexpressing strain and increased in the mt knockout strain compared with the wild-type strain. This work suggests that the malate transporter plays an important role in regulating lipid accumulation in oleaginous fungus M. circinelloides.
产油真菌中的脂肪酸生物合成需要还原力NADPH以及脂肪酸前体乙酰辅酶A的供应。乙酰辅酶A在细胞质中由ATP：柠檬酸裂解酶产生，而该酶需要柠檬酸通过柠檬酸/苹果酸/丙酮酸转运体从线粒体转运而来。这种位于线粒体内膜的转运体将细胞质中的苹果酸转运到线粒体中，以交换线粒体中的柠檬酸进入细胞质（图1）。然而，苹果酸转运体在产油真菌脂质积累中的作用尚未完全了解。因此，在产油真菌卷枝毛霉中操纵编码苹果酸转运体的mt基因的表达水平，以分析其对脂质积累的影响。结果表明，与对照菌株相比，mt基因过表达使脂质含量增加了约70%（从干细胞重量的13%增加到22%），而mt基因敲除突变体中的脂质含量降低了约27%（从干细胞重量的13%降低到9.5%）。此外，与野生型菌株相比，mt基因过表达菌株的细胞外苹果酸浓度降低，而mt基因敲除菌株的细胞外苹果酸浓度增加。这项研究表明，苹果酸转运体在调节产油真菌卷枝毛霉的脂质积累中起着重要作用。
